The integrated circuit is an assembly of electronic components--semiconductors, capacitors, resistors, and their interconnections--laid out on a substrate, or foundation, usually made of silicon. The integrated circuit is the heart of the modern personal computer.

The first integrated circuits were invented within months of each other in 1959-60 by two individuals working separately on the idea: Jack Kilby, an engineer at Texas Instruments, and Robert Noyce, a physicist at Fairchild Semiconductor. Noyce went on to become a founder of Intel Corporation, which refined and perfected the microprocessor--a large number of tiny transistors etched on a silicon chip--for use in small computers.

In 1975 the first personal computer, the Altair 8800, went on the market. It used an Intel 8800 microchip. This machine was followed within two years by a personal computer from Tandy Corporation, sold through its Radio Shack outlets; and the Apple Computer, designed by Stephen Wozniak and Stephen Jobs.

As computer technology expanded in the 1980s and 1990s, it touched many aspects of modern life, from business to personal use. Desktop computers, as most personal computers were called, were followed by portable "laptop" computers and notebook computers weighing less than seven pounds. Graphical user interfaces, or GUIs, became popular ways of accessing programs and files without the need for complex commands. By the